1. Field of the Invention
The present invention relates to monitoring carbon dioxide in an earth formation. In particular, the monitoring is performed in a borehole penetrating the earth formation.
2. Description of the Related Art
Injection of carbon dioxide (CO2) into earth formations known to contain reservoirs of hydrocarbons is being increasingly used to enhance recovery of the hydrocarbons. It is important to know the levels of CO2 in the formations to properly conduct the enhanced recovery. Thus, it is important to be able to monitor the levels of CO2.
Another application in which it is important to monitor the levels of CO2 is sequestration of CO2. Advanced coal burning electric generating plants are able to scrub CO2 from emissions. Because of various financial incentives, generating plants are investigating sequestering the CO2 in depleted reservoirs. Accordingly, the CO2 needs to be monitored to prevent its escape into the atmosphere.
Whether used for the enhanced recovery of hydrocarbons or the sequestration of CO2, boreholes provide an avenue for monitoring levels of CO2. Since the boreholes may be used repeatedly time and again, it is quite normal for those wells to go through some type of completion that will involve placement of casings for borehole stability. Unfortunately, such completions usually eliminate a significant portion of technologies from being used to monitor levels of CO2 from within a completed borehole.
Therefore, what are needed are techniques to monitor levels of CO2 from within a completed borehole.